In a typical lumber mill or planer mill, each board is moved along sideways. That is, oriented transversely on a lugged transfer prior to trimming or sorting. Typically, the lugs on the transfer are evenly spaced at precise intervals. Moving boards through an electronic scanner by the lugged transfer, the scanner determines the shape and/or length of each board and sends the information to an optimizer. The optimizer in turn sends the information to a controller. The controller activates saws above a trimer saw deck to trim the board in the corresponding lug space, in an attempt to maximize board utilization.
Typically, however, saws are spaced about two feet apart, so that depending upon the physical defects of a board, up to almost two feet on each end of the board can be trimmed and thus wasted, which can result in a considerable wastage of useful wood.
In order to minimize such wastage, in the prior art, board positioners have been developed which utilize a plurality of parallel rollers that are driven in a direction perpendicular to the transfer deck, thus moving the ends of the boards against a positioning fence. When on the rollers, the boards are continually thrust laterally across the transfer deck. The boards are elevated out of contact with the rollers at a predetermined time. Such devices suffer from the fact that tapered ends of the boards abutting the positioning fence can be so structurally weak as to collapse or break when driven against the fence by the rollers. Because the board has been optimized based on the inclusion of the tapered ends, if one end of the board is broken off, the optimized positioning of the board is adversely affected as the broken board is driven against the positioning fence, resulting in a board that is trimmed non-optimally.
Thus, it is the object of the present invention to provide a board positioning device which can accurately position selected boards lengthwise, and process the boards through the trimmer at a higher rate of speed than prior art devices, without collapse of the board's weak ends, to thus provide an improvement in maintaining a consistently accurate and optimally trimmed board.
Further, if the board is translated laterally by the rollers more than a small distance before the board contacts the positioning fence, the lateral velocity and acceleration of the board will often result in the board bouncing off the positioning fence. This also causes loss of accuracy in optimizing positioning of the board for trimming the optimizer and controller regulating the lateral optimized positioning of the board relative to the saws is based on the assumption that the board is ended closely against the positioning fence.
Thus, it is an object of the present invention to provide a board positioning device which can accurately position selected boards lengthwise, that is, transversely across the transfer deck and process the boards through the trimmer at a higher rate of speed than prior art devices. Controlled ending substantially reduces board bounce, and/or collapse of the board's weak ends, thus providing an improvement in maintaining a consistently accurate and optimally trimmed board.
It is yet another object of the present invention, to provide a stepped fence board positioning device for sorting of boards by length or grade.